D–A Conjugated Polymer/CdS S-Scheme Heterojunction with Enhanced Interfacial Charge Transfer for Efficient Photocatalytic Hydrogen Generation

Owing to the improved charge separation and maximized redox capability of the system, Step-scheme (S-scheme) heterojunctions have garnered significant research attention for efficient photocatalysis of H 2 evolution. In this work, an innovative linear donor–acceptor (D–A) conjugated polymer fluorene-alt-(benzo-thiophene-dione) (PFBTD) is coupled with the CdS nanosheets, forming the organic–inorganic S-scheme heterojunction. The CdS/PFBTD (CP) composite exhibits an impressed hydrogen production rate of 7.62 mmol g −1 h −1 without any co-catalysts, which is ≈14 times higher than pristine CdS. It is revealed that the outstanding photocatalytic performance is attributed to the formation of rapid electron transfer channels through the interfacial Cd─O bonding as evidenced by the density functional theory (DFT) calculations and in situ X-ray photoelectron spectroscopy (XPS) analysis. The charge transfer mechanism involved in S-scheme heterojunctions is further investigated through the photo-irradiated Kelvin probe force microscopy (KPFM) analysis. This work provides a new point of view on the mechanism of interfacial charge transfer and points out the direction of designing superior organic–inorganic S-scheme heterojunction photocatalysts.